U.S. patent number 6,348,253 [Application Number 09/500,503] was granted by the patent office on 2002-02-19 for sanitary pad for variable flow management.
This patent grant is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Jaime Braverman, Michael Allen Daley, Rebecca Lyn Dilnik, Ronald Lee Edens, Yvette Lynn Hammonds, Tamara Lee Mace, David Michael Matela, Alexander Manfred Schmidt-Foerst, Laura Jane Walker.
United States Patent |
6,348,253 |
Daley , et al. |
February 19, 2002 |
Sanitary pad for variable flow management
Abstract
There is provided a feminine hygiene pad comprising a cover
adjacent a capillarity fabric having regions of high and low
capillarity, which is adjacent a retention layer. In a preferred
embodiment, a creped spunbond layer is used as the cover material
and a co-apertured intake/distribution layer and transfer delay
layer are the capillarity fabric. Combining these improvements into
an integrated absorbent system allows the successful achievement of
variable flow management and a successful balance between intake
and cover desorption properties. The result is improved multiple
intake performance and a clean and dry cover surface during
use.
Inventors: |
Daley; Michael Allen
(Alpharetta, GA), Braverman; Jaime (Atlanta, GA), Dilnik;
Rebecca Lyn (Neenah, WI), Edens; Ronald Lee (Appleton,
WI), Hammonds; Yvette Lynn (Fond du Lac, WI), Mace;
Tamara Lee (Doraville, GA), Matela; David Michael
(Alpharetta, GA), Schmidt-Foerst; Alexander Manfred
(Erlangen, DE), Walker; Laura Jane (Appleton,
WI) |
Assignee: |
Kimberly-Clark Worldwide, Inc.
(Neenah, WI)
|
Family
ID: |
26825873 |
Appl.
No.: |
09/500,503 |
Filed: |
February 9, 2000 |
Current U.S.
Class: |
428/138; 428/131;
604/383; 604/385.01; 604/378; 428/137; 428/152; 604/358;
428/913 |
Current CPC
Class: |
A61F
13/53717 (20130101); A61F 13/512 (20130101); Y10T
428/24446 (20150115); Y10T 428/24322 (20150115); A61F
2013/15422 (20130101); A61F 2013/53782 (20130101); Y10S
428/913 (20130101); Y10T 428/24331 (20150115); Y10T
428/24273 (20150115); A61F 2013/15406 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61F 013/15 (); B32B
003/24 () |
Field of
Search: |
;428/137,138,131,152,913
;604/378,358,383,385.01 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
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1128704 |
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Aug 1982 |
|
CA |
|
0 124 365 |
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Nov 1984 |
|
EP |
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2044554 |
|
Feb 1971 |
|
FR |
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2 111 836 |
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Jul 1983 |
|
GB |
|
8164160 |
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Jun 1996 |
|
JP |
|
93/09745 |
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May 1993 |
|
WO |
|
95/07673 |
|
Mar 1995 |
|
WO |
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95/17870 |
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Jul 1995 |
|
WO |
|
96/33679 |
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Oct 1996 |
|
WO |
|
97/02133 |
|
Jan 1997 |
|
WO |
|
97/14384 |
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Apr 1997 |
|
WO |
|
97/18783 |
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May 1997 |
|
WO |
|
97/33546 |
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Sep 1997 |
|
WO |
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97/36565 |
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Oct 1997 |
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WO |
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97/45083 |
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Dec 1997 |
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WO |
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98/13003 |
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Apr 1998 |
|
WO |
|
98/22065 |
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May 1998 |
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WO |
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98/24960 |
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Jun 1998 |
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WO |
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Other References
Polymer Blends and Composites by John A. Manson and Leslie H.
Sperling, copyright 1976 by Plenum Press, a division of Plenum
Publishing Corporation of New York, IBSN 0-306-30831-2, at pp. 273
through 277. .
"Quantification of Unidirectional Fiber Bed Permeability" by J.
Westhuizen and J. P. Du Plessis in the Journal of Composite
Materials, 28(7), 1994..
|
Primary Examiner: Watkins, III; William P.
Attorney, Agent or Firm: Robinson; James B.
Parent Case Text
This application claims priority from U.S. Provisional Patent
Application No. 60/127,685 filed Apr. 3, 1999.
Claims
What is claimed is:
1. A feminine hygiene pad comprising a rapid intake cover adjacent
co-apertured intake/distribution and nonwoven transfer delay
layers, wherein said transfer delay layer enhances liquid
distribution in an X-Y plane of said pad and wherein said
co-aperturing produces apertures with walls wherein liquid can be
absorbed through the walls of said apertures, which is adjacent an
absorbent core retention layer.
2. The pad of claim 1 wherein said cover is made from a process
selected from the group consisting of spunbonding, meltblowing,
spunlacing, creping, film aperturing, foaming, airlaying,
coforming, bonding and carding, and combinations thereof.
3. The pad of claim 2 wherein said cover is made by a spunbond
process and has a basis weight between about 10 and 30 gsm and is
creped an amount between 20 and 50 percent.
4. The layer of claim 1 wherein said intake/distribution layer
horizontally wicks menses a distance of from about 1.2 cm to about
15.25 cm.
5. The pad of claim 1 wherein said transfer delay layer is adjacent
said absorbent core.
6. The pad of claim 1 wherein said transfer delay layer is a
material selected from the group consisting of spunbond fabric,
meltblown fabric, carded fabric and films.
7. The pad of claim 1 wherein said transfer delay layer is a
spunbond fabric with a basis weight between about 15 and 50
gsm.
8. The pad of claim 1 wherein said intake/distribution layer is a
material selected from the group consisting of airlaid fabric,
bonded carded webs, coform materials, hydroentangled pulp fabrics
and meltblown fabrics.
9. The pad of claim 8 wherein said intake/distribution layer is an
airlaid fabric having a basis weight between about 100 and 300 gsm
and a density between about 0.05 and 0.18 g/cc.
10. The pad of claim 1 wherein said intake/distribution and
transfer delay layers are co-apertured with pins at a density of
between about 1.6 and 6.2 pins/cm.sup.2.
11. The pad of claim 1 wherein said intake/distribution and
transfer delay layers are co-apertured with pins at a density of
about 2.5 pins/cm.sup.2.
12. The layer of claim 1 wherein said absorbent core comprises pulp
and superabsorbent.
13. The pad of claim 12 wherein said superabsorbent is in a form
selected from the group consisting of flakes, particles, spheres,
foams and fibers.
14. A feminine hygiene pad comprising a creped spunbond nonwoven
fabric outer cover adjacent a pulp airlaid fabric
intake/distribution layer having a basis weight between about 175
and 225 gsm and a density between about 0.08 and 0.14 g/cc,
co-apertured at a pin density of between about 1.6 and 6.2
pins/cm.sup.2 to a polyolefin spunbond nonwoven fabric transfer
delay layer having a basis weight between about 25 and 35 gsm,
adjacent a retention layer comprising pulp and superabsorbent
material.
15. The pad of claim 14 wherein said cover is creped an amount
between about 25 and 40 percent and has a basis weight between
about 15 and 25 gsm.
16. The pad of claim 14 wherein said airlaid fabric is made from
pulp and thermoplastic fibers.
17. The pad of claim 14 wherein said spunbond fabric is made from
polypropylene fibers.
18. The pad of claim 14 wherein said creped cover is made from
polypropylene fibers.
Description
FIELD OF THE INVENTION
The present invention is an absorbent article for personal care,
particularly feminine hygiene products, which can accept liquid,
distribute it and retain it.
BACKGROUND OF THE INVENTION
Personal care articles include such items as diapers, training
pants, feminine hygiene products such as sanitary napkins,
panty-liners and tampons, incontinence garments and devices,
bandages and the like. The most basic design of all such articles
typically includes a bodyside liner, an outercover (also referred
to as a baffle) and an absorbent core disposed between the bodyside
liner and the outercover.
Personal care products must accept fluids quickly and hold them to
reduce the possibility of leakage outside the product. The product
must be flexible and have a pleasing feel on the skin, and even
after liquid insult, must not become tight or bind the user.
Unfortunately, while previous products have met many of these
criteria to varying degrees, a number have not.
In particular, feminine hygiene products for longer term (i.e.
overnight) usage are subject to higher and more variable flow rates
and fluid loads than are those intended for regular or shorter term
usage. Products for overnight usage, therefore, must have the
ability to absorb and contain continuous and light flow as well as
gushes and sudden heavy flow over the life of the product. It has
been found that continuous flow insults in feminine hygiene
products average 1 ml/hr, but may be higher, and are not literally
continuous or constant, but rather variable in rate and may even
pause during a cycle. "Gush flow" is defined as a sudden heavy flow
condition and occurs at flow rates of up to 1 ml/sec. During a
gush, 1-5 ml of fluid is released from the body onto the product.
The term "continuous flow" is used to define any flow which falls
outside of the definition of gush flow.
Combining continuous and gush flow conditions results in variable
flow. Essentially, "variable flow" is defined as continuous flow
with intermittent gush flow occurrences. FIG. 1 is a graph which
illustrates the differences between variable flow (diamonds) and
continuous flow (squares) over the life of a single product where
flow rate volume is on the y-axis in g/hr and time is on the x-axis
in hours. This problem of handling gush and continuous flows is
termed variable flow management and is defined as the ability to
absorb and contain continuous and light flow (1-2 ml/hr) as well as
multiple gushes or sudden heavy flow insults (1 ml/sec with a total
volume of 1-5 ml) over the life of the product. It is obvious that
the challenge of variable flow management is more difficult as the
wear time of the product is lengthened, such as in overnight use
conditions.
Many feminine care cover materials have low z-directional
conductivity, low surface energy, low void volume, and provide
little separation between the absorbent core and the user due to
their two dimensional structure. Consequently, these covers result
in slow and incomplete intake, high rewet, and large surface
stains. In addition, typical intake or acquisition layers are low
density, high void volume structures which are ideal for fast fluid
intake, but because these structures typically have low
capillarity, fluid is not adequately desorbed from the cover
material, resulting in smearing and surface wetness. Materials
which enhance cover desorption are typically high density, high
capillarity materials, but because these materials have low void
volume and low z-directional permeability, they inherently retard
fluid intake.
There remains a need to address variable flow management from the
overall product form standpoint, developing a system in which the
components are optimized to function together. In such a system,
the liner is designed to promote rapid intake and remain clean and
dry, there is an intake/distribution material which has the void
volume necessary for fast intake and the high capillarity desired
for sufficient cover desorption while maintaining an appropriate
capillary structure for fluid intake/distribution and the absorbent
(retention) layer accepts fluids at the appropriate speed.
An objective of this invention is, therefore, to provide an overall
design for a feminine hygiene product, particularly for overnight
use, to manage a wide variety of flow conditions including sudden
heavy flow insults, or gushes.
SUMMARY OF THE INVENTION
The objects of the invention are achieved by a creped spunbond
nonwoven fabric for use as the liner or outer cover, an improved
absorbent core using a co-apertured airlaid fabric layer and
spunbond nonwoven fabric transfer delay layer, over a fluff
retention layer. Combining these improvements into an integrated
absorbent system allows the successful achievement of variable flow
management and a successful balance between intake and cover
desorption properties. The result is improved multiple intake
performance and a clean and dry cover surface during use. The
material technology developments regarding variable flow management
focus on attaining the proper material structure and property
balance necessary to achieve fast intake and improve cover
desorption, cover staining, and rewet characteristics. These
functional properties are provided through improved material
technologies and product construction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph of variable flow (diamonds) and continuous flow
(squares) over the life of a single product where flow rate volume
is on the y-axis in g/hr and time is on the x-axis in hours.
FIG. 2 illustrates the tri-modal pore structure of the co-apertured
material.
FIGS. 3, 4, and 5 display SEM images of the apertures. FIG. 3
displays an aperture on the airlaid side of the composite. FIG. 4
displays a close-up of an aperture on the airlaid side of the
composite and FIG. 5 displays an aperture from the spunbond
(transfer delay) side of the composite.
FIG. 6 compares the pore size distribution of an apertured airlaid
material to a un-apertured airlaid material.
FIG. 7 illustrates the detail of a single aperture and the flow
through the material.
FIG. 8 is a graph of the pore size distribution for creped and
uncreped spunbond cover materials.
FIG. 9 shows the three dimensional structure of the creped spunbond
fabric cover in an SEM image.
FIG. 10 depicts one example of a product form for a feminine
hygiene product for overnight use.
FIG. 11 illustrates the theoretical fluid loading profile for the
feminine hygiene product of FIG. 10.
FIG. 12 shows a pin aperturing pattern at 7.4 pins/cm.sup.2 using
2.06 mm diameter pins.
FIG. 13 shows a pin aperturing pattern at 2.5 pins/cm.sup.2 with
the same pin diameter as FIG. 12.
FIG. 14 is a graph the measured capacity for airlaid fabrics with
and without apertures where capacity is on the Y-axis and fabric
density (cc/g) on the X-axis.
FIG. 15 is a graph of horizontal wicking distance (Y-axis) in mm
versus time in minutes for two apertured and two un-apertured
airlaid fabrics.
FIG. 16 is a graph of saturation in g/g (Y-axis) versus horizontal
wicking distance in inches.
FIG. 17 is a graph of saturation in g/g (Y-axis) versus the pad
section as divided according to the flat system fluid distribution
test.
FIG. 18 is a graph of saturation in gig (Y-axis) versus the pad
section as divided according to the flat system fluid distribution
test.
FIGS. 19, 20 and 21 are bar charts of triple gush insult results on
various parts of a pad.
DEFINITIONS
"Disposable" includes being disposed of after use and not intended
to be washed and reused.
"Layer" when used in the singular can have the dual meaning of a
single element or a plurality of elements.
"Liquid" means a non-particulate substance and/or material that
flows and can assume the interior shape of a container into which
it is poured or placed.
"Liquid communication" means that liquid is able to travel from one
layer to another layer, or one location to another within a
layer.
"Longitudinal" means having the longitudinal axis in the plane of
the article and is generally parallel to a vertical plane that
bisects a standing wearer into left and right body halves when the
article is worn. The "transverse" axis lies in the plane of the
article generally perpendicular to the longitudinal axis, i.e., so
that a vertical plane bisects a standing wearer into front and back
body halves when the article is worn.
"Conjugate fibers" refers to fibers that have been formed from at
least two polymers extruded from separate extruders but spun
together to form one fiber. Conjugate fibers are also sometimes
referred to as multicomponent or bicomponent fibers. The polymers
are usually different from each other though conjugate fibers may
be monocomponent fibers. The polymers are arranged in substantially
constantly positioned distinct zones across the cross-section of
the conjugate fibers and extend continuously along the length of
the conjugate fibers. The configuration of such a conjugate fiber
may be, for example, a sheath/core arrangement wherein one polymer
is surrounded by another or may be a side by side arrangement, a
pie arrangement or an "islands-in-the-sea" arrangement. Conjugate
fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S.
Pat. No. 5,336,552 to Strack et al., and U.S. Pat. No. 5,382,400 to
Pike et al. For two component fibers, the polymers may be present
in ratios of 75/25, 50/50, 25/75 or any other desired ratios. The
fibers may also have shapes such as those described in U.S. Pat.
No. 5,277,976 to Hogle et al., and U.S. Pat. Nos. 5,069,970 and
5,057,368 to Largman et al., hereby incorporated by reference in
their entirety, which describe fibers with unconventional
shapes.
"Biconstituent fibers" refers to fibers that have been formed from
at least two polymers extruded from the same extruder as a blend.
Biconstituent fibers do not have the various polymer components
arranged in relatively constantly positioned distinct zones across
the cross-sectional area of the fiber and the various polymers are
usually not continuous along the entire length of the fiber,
instead usually forming fibrils or protofibrils which start and end
at random. Biconstituent fibers are sometimes also referred to as
multiconstituent fibers. Fibers of this general type are discussed
in, for example, U.S. Pat. No. 5,108,827 to Gessner. Bicomponent
and biconstituent fibers are also discussed in the textbook Polymer
Blends and Composites by John A. Manson and Leslie H. Sperling,
copyright 1976 by Plenum Press, a division of Plenum Publishing
Corporation of New York, IBSN 0-306-30831-2, at pages 273 through
277.
As used herein, the term "machine direction" or MD means the length
of a fabric in the direction in which it is produced. The term
"cross machine direction" or CD means the width of fabric, i.e. a
direction generally perpendicular to the MD.
As used herein the term "spunbonded fibers" refers to small
diameter fibers which are formed by extruding molten thermoplastic
material as filaments from a plurality of fine, usually circular
capillaries of a spinneret with the diameter of the extruded
filaments then being rapidly reduced as by, for example, in U.S.
Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to
Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S.
Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No.
3,502,763 to Hartman, and U.S. Pat. No. 3,542,615 to Dobo et al.
Spunbond fibers are generally not tacky when they are deposited
onto a collecting surface. Spunbond fibers are generally continuous
and have average diameters (from a sample of at least 10) larger
than 7 microns, more particularly, between about 10 and 35 microns.
The fibers may also have shapes such as those described in U.S.
Pat. No. 5,277,976 to Hogle et al., U.S. Pat. No. 5,466,410 to
Hills and U.S. Pat. Nos. 5,069,970 and 5,057,368 to Largman et al.,
which describe fibers with unconventional shapes.
As used herein the term "meltblown fibers" means fibers formed by
extruding a molten thermoplastic material through a plurality of
fine, usually circular, die capillaries as molten threads or
filaments into converging high velocity, usually hot, gas (e.g.
air) streams which attenuate the filaments of molten thermoplastic
material to reduce their diameter, which may be to microfiber
diameter. Thereafter, the meltblown fibers are carried by the high
velocity gas stream and are deposited on a collecting surface to
form a web of randomly dispersed meltblown fibers. Such a process
is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin et
al. Meltblown fibers are microfibers that may be continuous or
discontinuous, are generally smaller than 10 microns in average
diameter, and are generally tacky when deposited onto a collecting
surface.
"Airlaying" is a well-known process by which a fibrous nonwoven
layer can be formed. In the airlaying process, bundles of small
fibers having typical lengths ranging from about 3 to about 52
millimeters are separated and entrained in an air supply and then
deposited onto a forming screen, usually with the assistance of a
vacuum supply. The randomly deposited fibers then are bonded to one
another using, for example, hot air or a spray adhesive. Examples
of airlaying technology can be found in U.S. Pat. Nos. 4,494,278,
5,527,171, 3,375,448 and 4,640,810.
As used herein, the term "coform" means a process in which at least
one meltblown diehead is arranged near a chute through which other
materials are added to the web while it is forming. Such other
materials may be pulp, superabsorbent or other particles, natural
polymers (for example, rayon or cotton fibers) and/or synthetic
polymers (for example, polypropylene or polyester) fibers, for
example, where the fibers may be of staple length. Coform processes
are shown in commonly assigned U.S. Pat. No. 4,818,464 to Lau and
U.S. Pat. No. 4,100,324 to Anderson et al. Webs produced by the
coform process are generally referred to as coform materials.
"Bonded carded web" refers to webs that are made from staple fibers
that are sent through a combing or carding unit, which opens and
aligns the staple fibers in the machine direction to form a
generally machine direction-oriented fibrous nonwoven web. The web
is bonded by one or more of several known bonding methods.
Bonding of nonwoven webs may be achieved by a number of methods;
powder bonding, wherein a powdered adhesive is distributed through
the web and then activated, usually by heating the web and adhesive
with hot air; pattern bonding, wherein heated calender rolls or
ultrasonic bonding equipment are used to bond the fibers together,
usually in a localized bond pattern, though the web can be bonded
across its entire surface if so desired; through-air bonding,
wherein air which is sufficiently hot to soften at least one
component of the web is directed through the web; chemical bonding
using, for example, latex adhesives that are deposited onto the web
by, for example, spraying; and consolidation by mechanical methods
such as needling and hydroentanglement.
An intake/distribution layer is a material which can wick menstrual
fluid a distance of 1.2 cm to about 15.25 cm (0.5 to 6 inches) in
one hour when one end of the material is placed in an infinite
reservoir of menstrual simulant.
"Co-aperture" refers to a material which has been apertured, as
well as a process of aperturing, wherein two or more materials are
apertured together. The apertures extend from top to bottom of the
material and are essentially aligned with each other. Co-aperturing
can join the materials either temporarily or permanently through
entanglement, physical bonding or chemical bonding. It is preferred
that co-aperturing be carried out at ambient temperatures, not at
elevated temperatures.
"Personal care product" means diapers, training pants, absorbent
underpants, adult incontinence products, swim wear, bandages and
other wound dressings, and feminine hygiene products.
"Feminine hygiene products" means sanitary napkins and pads.
"Target area" refers to the area or position on a personal care
product where an insult is normally delivered by a wearer.
TEST METHODS
Material Caliper (thickness)
The caliper of a material is a measure of thickness and is measured
at 0.05 psi (3.5 g/cm.sup.2) with a Starret-type bulk tester, in
units of millimeters.
Density
The density of the materials is calculated by dividing the weight
per unit area of a sample in grams per square meter (gsm) by the
material caliper in millimeters (mm) at 0.05 psi (3.5 g/cm.sup.2)
and multiplying the result by 0.001 to convert the value to grams
per cubic centimeter (g/cc). A total of three samples would be
evaluated and averaged for the density values.
Triple Intake Test Procedure
The objective of this test is to determine differences between
materials and/or materials, composites or systems of material
composites in the rate of intake when 3 fluid insults are applied,
with time allowed for fluid to distribute in the material(s)
between insults.
Equipment Needed:
2 acrylic rate blocks.
P-5000 pipette with RC-5000 tips and foam pipette insert.
Small beaker
Menses simulant (made according to directions below), warmed in
bath for 30 minutes or more
Small spatula (stirrer)
Bench liner
2 stopwatches
1-2 timers
Gauze squares for cleaning simulant
Procedure: Lay out sample composites according to materials testing
plan.
Components are as Follows:
Top: Cover
Middle: Capillarity fabric
Bottom: Retention Layer
Weigh each layer dry, record weight. Put materials back in 3-layer
composite. Weigh a dry blotter, record weight and also mark weight
on blotter. Place acrylic rate block in middle of sample
composite.
Calibrate Pipette:
Weigh a small empty beaker on the balance.
Set pipette to 2 mls.
Draw Simulant into Pipette.
Deliver simulant from pipette into beaker. If balance indicates 2
grams of simulant was delivered, setting is correct. If more or
less than 2 grams was delivered, decrease or increase the setting
and repeat adjusting pipette and weighing the amount of simulant
delivered until 2 grams is delivered.
Simulant Handling:
Remove simulant from the refrigerator 30 minutes to 1 hour before
using and warm in water bath. Before cutting bag nozzle, massage
the bag between hands for a few minutes to mix the simulant, which
will have separated in the bag. Cut the bag tubing and pour
simulant needed into a small beaker. Stir slowly with a small
spatula to mix thoroughly. Return bag to the refrigerator if you do
not anticipate using all of it. Return bag to water bath if more
will be used during the day.
Test:
Step 1: Center acrylic rate block with funnel on sample. Insult
sample composite with 2 mls. simulant, using stopwatch to measure
the time from the start of the insult until the fluid is absorbed
beneath the cover material. Leave rate block in place for 9
minutes, (use timer). For first sample, after 9 minutes remove the
rate block and weigh each layer of the sample. Record the weight.
(After 3 minutes timing of the first sample, start testing a second
sample going through the same steps.)
Step 2: For the first sample, repeat Step 1 a second time.
Step 3: For the first sample, repeat Step 1 a third time.
Analysis: The fluid loading in each component is calculated as
weight after insult subtracted from the weight before insult. The
insult time is a direct measurement of time for absorption. Smaller
values of intake time refer to a more absorbent sample with larger
values of intake time refer to a less absorbent sample.
Capacity
Capacity was measured using the dunk and drip capacity test method.
Menses simulant was used as the test fluid. The sample size was
modified to a 5.7 cm (2.25") diameter circle. The weight of each
sample was recorded. The sample was immersed in a bath of simulant
until equilibration, in this case 9 minutes. The sample was removed
from the bath and hung vertically at a height of 10.5 cm (12
inches) using a small clip for 10 minutes. The sample was weighed
and the weight was recorded. The capacity was determined by
subtracting the before weight from the after weight. The capacity
in grams/gram was determined by dividing the capacity in grams by
the dry weight of the sample.
Horizontal Capillary Wicking Test Procedure
The objective of this test it to determine the horizontal wicking
capability of a material as it pulls fluid from a infinite
reservoir. Equipment needed: Horizontal wicking stand, menses
simulant prepared as described below, ruler, timer.
Procedure:
Cut materials to 1" (2.54 cm) width and desired length.
Fill reservoir in horizontal wicking apparatus with menses
simulant.
Place one end of the material in the simulant and lay the rest of
the material on the wicking apparatus.
Start the timer.
Measure the distance wicked at a given time, or the time to wick to
a given distance.
Flat System Testing Procedure
The purpose of this procedure is to determine the fluid handling
characteristics of various absorbent systems through analysis of
stain length, saturation capacity, and the fluid loading of the
system components. The equipment required includes hourglass-shaped
acrylic plates (with a 0.25 inch hole in the center) weighing
approximately 330 grams, syringes, one-eighth inch I.D. Tygon
tubing, pipette pump, menses simulant, and a laboratory balance
(accurate to 0.00 g).
Samples to be tested are cut to a desired shape (currently 1.5
inches by 5.5 inches for fluid intake/distribution layers or
capillarity fabrics, 1.75 inches by 5.5 inches for transfer delay
layers, and 200 mm long hourglass shape for retention layers). The
5.5 inch layers are marked into 1.1 inch sections and the pad layer
is marked into sections corresponding to the marks on the 5.5 inch
layers when they are centered on the pad layer. Each component is
weighed and the weight recorded. The individual components are
assembled in to a desired component system maintaining the marked
sections aligned and one end is labeled as the top. Syringes are
filled with menses simulant and Tygon tubing attached to the
syringes. The syringes are raced in a pipette pump which is
programmed to deliver a given amount of simulant, currently 30 cc
syringes dispensing a specified amount of simulant (usually 10 ml)
in one hour. With the open ends of the tubing placed in a beaker,
the tubing is primed by running the pump until all air is out of
the tubing and simulant is exiting the tubing at the insult end.
The component systems to be tested are placed near the pipette pump
and a two inch by six inch piece of 25 gsm, 10 d BCW is placed on
top of the center of the system over which an acrylic plate is
placed, also centered on top of the system. The free end of one
tubing is inserted into the hole in the acrylic plate and the
pipette pump started to begin the insults. At the end of the insult
period, the tubing and acrylic plates are removed. The BCW is then
carefully removed without moving the underlying layers and
discarded. Each layer is then individually weighed and the weight
recorded. Then, beginning at the end labeled as the top, each
marked section is cut and weighed. The stain length for each layer
is measured and recorded and the data entered into a spreadsheet
for graphing and analysis. The fluid loading (g/g) is calculated by
dividing the amount of fluid absorbed in a material by the dry
weight of the material. The fluid saturation is calculated by
dividing the fluid loading by the stain length.
Demand Absorbency Wicking Capability
The objective of this test is to determine the fluid handling
characteristics of various absorbent systems through analysis of
stain length, saturation capacity, and fluid loadings of the system
components.
Equipment needed: Hourglass-shaped acrylic plates (with 0.25" (6.35
mm) hole in the center) weighing approximately 330 grams; syringes;
1/8 inch (3.175 mm) internal diameter (ID) tubing (e.g.
Tygon.RTM.); pipette pump; menses simulant prepared as described
below; laboratory balance (accurate to 0.00 g).
Procedure:
1. Cut components to desired shape; 1.5 inches (3.8 cm) by 6.0
inches (15.2 cm) for intake/distribution layers, 3.0 inches (7.6
cm) by 6.0 inches for spunbond nonwoven fabric transfer delay and
perimeter layers.
2. Mark 6.0 inch layers into 1.2 inch (3 cm) sections. If the
perimeter layer is oval, mark into sections corresponding to the
marks on the intake/distribution strip when centered on the
perimeter layer.
3. Weigh each component and record the weight.
4. Assemble the individual components into the desired absorbent
system keeping the marked sections aligned. Label one end as the
top.
5. Fill the syringes with menses simulant and attach tubing to
syringes.
6. Place the syringes in the syringe pump.
7. Program the size of the syringe into the syringe pump.
8. Program the pump (currently using 30 cc syringes dispensing at a
rate of 10 ml. per hour.
9. With the open ends of the tubing placed in a beaker, prime
tubing by running pump until all air is out of tubing and simulant
is exiting the tubing at the open end.
10. Place the component systems to be tested near the syringe pump,
place a 2 inch (5.1 cm) by 6 inch (approximately) piece of 25 gsm,
10 denier bonded carded web material on the top layer of the
absorbent system to prevent wicking on the acrylic plate, and place
an acrylic plate centered on the top of the system.
11. Insert the open end of one tubing into the hole in the acrylic
plate. Repeat for the remaining systems to be tested.
Testing:
1. Start the pipette pump to begin the insult.
2. Ad 3 mls. of menses simulant at a rate of 10 mls per hour.
3. After 3 mls have been insulted into the product, add weights to
the acrylic plate to achieve a pressure of 0.08 psi.
4. Continue the insults for another 5 mls, so that a TOTAL of 8 mls
is insulted.
5. At the end of the insult period, remove the tubing and acrylic
plates. Carefully remove the bonded carded web without moving the
underlying layers and discard it.
6. Take photos of the component system and layers and print
them.
7. Weigh each layer individually and record the weight.
8. Beginning at the end labeled as the top, cut and weigh the first
marked sections and the weight. Repeat for remaining sections and
layers.
9. Measure and record the stain length for each layer.
10. Enter the data in a spreadsheet for graphing and analysis.
Preparation of Menses Simulant
In order to prepare the fluid, blood, in this case defibrinated
swine blood, was separated by centrifugation at 3000 rpm for 30
minutes, though other methods or speeds and times may be used if
effective. The plasma was separated and stored separately, the
buffy coat removed and discarded and the packed red blood cells
stored separately as well.
Eggs, in this case jumbo chicken eggs, were separated, the yolk and
chalazae discarded and the egg white retained. The egg white was
separated into thick and thin portions by straining the white
through a 1000 micron nylon mesh for about 3 minutes, and the
thinner portion discarded. Note that alternative mesh sizes may be
used and the time or method may be varied provided the viscosity is
at least that required. The thick portion of egg white which was
retained on the mesh was collected and drawn into a 60 cc syringe
which was then placed on a programmable syringe pump and
homogenized by expelling and refilling the contents five times. In
this example, the amount of homogenization was controlled by the
syringe pump rate of about 100 ml/min, and the tubing inside
diameter of about 0.12 inches. After homogenizing the thick egg
white had a viscosity of about 20 centipoise at 150 sec.sup.-1 and
it was then placed in the centrifuge and spun to remove debris and
air bubbles at about 3000 rpm for about 10 minutes, though any
effective method to remove debris and bubbles may be used.
After centrifuging, the thick, homogenized egg white, which
contains ovamucin, was added to a 300 cc Fenwal.RTM. Transfer pack
using a syringe. Then 60 cc of the swine plasma was added to the
transfer pack. The transfer pack was clamped, all air bubbles
removed, and placed in a Stomacher lab blender where it was blended
at normal (or medium) speed for about 2 minutes. The transfer pack
was then removed from the blender, 60 cc of swine red blood cells
were added, and the contents mixed by hand kneading for about 2
minutes or until the contents appeared homogenous. A hematocrit of
the final mixture showed a red blood cell content of about 30
weight percent and generally should be at least within a range of
28-32 weight percent for artificial menses made according to this
example. The amount of egg white was about 40 weight percent.
The ingredients and equipment used in the preparation of this
artificial menses are readily available. Below is a listing of
sources for the items used in the example, though of course other
sources may be used providing they are approximately
equivalent.
Blood (swine): Cocalico Biologicals, Inc., 449 Stevens Rd.,
Reamstown, Pa. 17567, (717) 336-1990.
Fenwal.RTM. Transfer pack container, 300 ml, with coupler, sample
4R2014: Baxter Healthcare Corporation, Fenwal Division, Deerfield,
Ill. 60015.
Harvard Apparatus Programmable Syringe Pump model no. 55-4143:
Harvard Apparatus, South Natick, Mass. 01760.
Stomacher 400 laboratory blender model no. BA 7021, serial no.
31968: Seward Medical, London, England, UK.
1000 micron mesh, item no. CMN-1000-B: Small Parts, Inc., PO Box
4650, Miami Lakes, Fla. 33014-0650, 1-800-220-4242.
Hemata Stat-II device to measure hemocrits, serial no. 1194Z03127:
Separation Technology, Inc., 1096 Rainer Drive, Altamont Springs,
Fla. 32714.
Rate Block Intake Test
This test is used to determine the intake time of a known quantity
of fluid into a material and/or material system. The test apparatus
consists of a rate block 10 as shown in FIG. 1. A 4".times.4" piece
of absorbent 14 and cover 13 are die cut. The specific covers are
described in the specific examples. The absorbent used for these
studies was standard and consisted of 250 g/m.sup.2 airlaid made of
90% Coosa 0054 and 10% HC T-255 binder. The total density for this
system was 0.10 g/cc. The cover 13 was placed over the absorbent 14
and the rate block 10 was placed on top of the two materials. 2 mL
of a menses simulant was delivered into the test apparatus funnel
11 and a timer started. The fluid moved from the funnel 11 into a
channel 12 where it was delivered to the material or material
system. The timer was stopped when all the fluid was absorbed into
the material or material system as observed from the chamber in the
test apparatus. The intake time for a known quantity of known fluid
was recorded for a given material or material system. This value is
a measure of a material or material systems absorbency. Typically,
five to ten repetitions were performed, and average intake time was
determined.
Rewet Test
This test is used to determine the amount of fluid that will come
back to the surface when a load is applied. The amount of fluid
that comes back through the surface is called the "rewet" value.
The more fluid that comes to the surface, the larger the "rewet"
value. Lower rewet values are associated with a dryer material and,
thus, a dryer product. In considering rewet, three properties are
important: (1) intake, if the material/system does not have good
intake then fluid can rewet, (2) ability of absorbent to hold fluid
(the more the absorbent holds on to the fluid, the less is
available for rewet), and (3) flowback, the more the cover
prohibits fluid from coming back through the cover, the lower the
rewet. In our case, we evaluated cover systems where the absorbent
was maintained constant and, thus, we were only concerned with
properties (1) and (3), intake and flowback, respectively.
A 4".times.4" piece of absorbent and cover was die cut. The
absorbent used for these studies was standard and consisted of a
250 g/m.sup.2 airlaid made of 90% Coosa 0054 and 10% HC T-255
binder. The total density for this system was 0.10 g/cc. The cover
was placed over the absorbent and the rate block was placed on top
of the two materials. In this test, 2 mL of menses simulant are
insulted into the rate block apparatus and are allowed to absorb
into a 4".times.4" sample of the cover material which is placed on
top of a 4".times.4" absorbent piece. The fluid is allowed to
interact with the system for one minute and the rate block rests on
top of the materials. The material system cover and absorbent are
placed onto a bag filled with fluid. A piece of blotter paper is
weighed and placed on top of the material system. The bag is
traversed vertically until it comes into contact with an acrylic
plate above it, thus pressing the whole material system against the
plate blotter paper side first. The system is pressed against the
acrylic plate until a total pressure of 1 psi is applied. The
pressure is held fixed for three minutes, after which the pressure
is removed and the blotter paper is weighed. The blotter paper
retains any fluid that was transferred to it from the
cover/absorbent system. The difference in weight between the
original blotter and the blotter after the experiment is known as
the "rewet" value. Typically, five to ten repetitions of this test
were performed, and average rewet was determined.
Intake/Staining Test
An intake/staining test was developed which enables the stain size,
intensity, and fluid retention in components to be observed with
fluid flow rate and pressure. Menses simulant was used as the test
fluid. A 4".times.4" piece of absorbent and cover were die cut. The
absorbent used for these tests was standard and consisted of a 250
g/m.sup.2 airlaid made of 90% of Coosa 0054 and 10% HC T-255
binder. The total density for this system was 0.10 g/cc. A material
system, cover and core measuring 4".times.4", was placed underneath
an acrylic plate with an 1/8 inch diameter hole bored into the
center. A piece of 1/8 inch tubing was connected to the hole with a
fitting. Menses simulant was delivered to the sample using a
syringe pump at a specified rate and for a specified volume. The
pump was programmed to deliver a total volume of 1 mL to the
samples, where the samples were under pressures of 0 psi, 0.0078
psi, and 0.078 psi. These pressures were applied using a weight
which was placed on top of the acrylic plates and distributed
evenly. The flow rate of the pump was programmed to deliver fluid
at a rate of 1 mL/sec. The stain size for the cover materials was
measured manually, and the amount of fluid in each component of the
system was measured by weight before and after absorption of the
fluid. The stain intensity was evaluated qualitatively by
comparison of samples. Staining information was recorded using a
digital camera and could be further analyzed with image
analysis.
Permeability
Permeability is obtained from a measurement of the resistance by
the material to the flow of liquid. A liquid of known viscosity is
forced through the material of a given thickness at a constant flow
rate and the resistance to flow, measured as a pressure drop is
monitored. Darcy's Law is used to determine permeability as
follows:
where the units are:
permeability: cm.sup.2 or darcy 1 darcy=9.87.times.10.sup.-9
cm.sup.2
flow rate: cm/sec
viscosity: pascal-sec
pressure drop: pascals
The apparatus consists of an arrangement wherein a piston within a
cylinder pushes liquid through the sample to be measured. The
sample is clamped between two aluminum cylinders with the cylinders
oriented vertically. Both cylinders have an outside diameter of
3.5", an inside diameter of 2.5" and a length of about 6". The 3"
diameter web sample is held in place by its outer edges and hence
is completely contained within the apparatus. The bottom cylinder
has a piston that is capable of moving vertically within the
cylinder at a constant velocity and is connected to a pressure
transducer that capable of monitoring the pressure of encountered
by a column of liquid supported by the piston. The transducer is
positioned to travel with the piston such that there is no
additional pressure measured until the liquid column contacts the
sample and is pushed through it. At this point, the additional
pressure measured is due to the resistance of the material to
liquid flow through it.
The piston is moved by a slide assembly that is driven by a stepper
motor. The test starts by moving the piston at a constant velocity
until the liquid is pushed through the sample. The piston is then
halted and the baseline pressure is noted. This corrects for sample
buoyancy effects. The movement is then resumed for a time adequate
to measure the new pressure. The difference between the two
pressures is the pressure due to the resistance of the material to
liquid flow and is the pressure drop used in Equation (1). The
velocity of the piston is the flow rate. Any liquid whose viscosity
is known can be used, although a liquid that wets the material is
preferred since this ensures that saturated flow is achieved. The
measurements disclosed herein were carried out using a piston
velocity of 20 cm/min, mineral oil (Peneteck Technical Mineral Oil
manufactured by Penreco of Los Angeles, Calif.) of a viscosity of 6
centipoise.
Alternatively, permeability can be calculated from the following
equation:
where R=fiber radius and
Reference for Equation (2) can be found in the article
"Quantification of Unidirectional Fiber Bed Permeability" by J.
Westhuizen and J. P. Du Plessis in the Journal of Composite
Materials, 28(7), 1994. Note that the equations show that
permeability can be determined if fiber radius, web density and
fiber density are known.
Conductance is calculated as permeability per unit thickness and
gives measure of the openness of a particular structure and, thus,
an indication of the relative ease at which a material will pass
liquid. The units are darcies/mil.
DETAILED DESCRIPTION OF THE INVENTION
In its broadest embodiment, the invention is feminine hygiene pad
comprising a rapid intake cover adjacent a capillarity fabric
having regions of varying capillarity which allows the passage of
fluids in particular areas, and which is adjacent an absorbent core
retention layer. The fabrics used in the practice of this invention
may be made by a variety of processes including airlaying,
spunbonding, meltblowing, carding, coform and foaming processes,
though airlaying for the intake/distribution layer and spunbonding
for the transfer delay layer are preferred. The various layers may
be made from synthetic polymer and natural fibers. Particularly
preferred because of cost are polyolefins like polyethylene and
polypropylene.
It is important that the cover rapidly draw insults into the
product. A number of materials provide such intake properties.
These include pin apertured films, vacuum apertured films,
apertured nonwovens and co-apertured film/nonwoven laminates,
conjugate fiber spunbond fabrics, creped spunbond fabrics, airlaid
fabrics, bonded carded webs, spunlace fabrics, etc. A number of
fabric types which may be unsuitable initially may be made
acceptable through the use of topical chemical treatments and
mechanical processing. Any material which, when combined with an
absorbent core, permits rapid intake, low staining, low rewet and
low fluid retention under all flow conditions would be
suitable.
The capillarity fabric is an intake/distribution layer which may be
made from a variety of fibers and mixtures of fibers including
synthetic fibers, natural fibers including, mechanically and
chemically softened pulp, staple fibers, slivers, meltblown and
spunbond fibers, superabsorbents and the like. The fibers in such a
web may be made from the same or varying diameter fibers and may be
of different shapes such as pentalobal, trilobal, elliptical,
round, etc. The intake/distribution layer may be made by a number
of methods, including airlaying, hydroentangling, bonding and
carding, and coforming, though airlaying is preferred.
The transfer delay layer may also be made from a variety of fibers
in a variety of shapes and sizes. The transfer delay layer may be
made according to a number of processes such as spunbonding,
carding, meltblowing and film forming, though spunbonding is
preferred.
The retention layer materials may be made from materials or
substances known in the art to absorb liquid as well as any others
that may be developed for that purpose. Examples include fast and
slow superabsorbents, pulps, and mixtures thereof. Mixtures of
superabsorbents and pulp used as retention materials may be used in
ratios of between about 100/0 and 0/100 by weight, more
particularly between about 80/20 and 20/80.
Synthetic fibers include those made from polyamides, polyesters,
rayon, polyolefins, acrylics, superabsorbents, Lyocel regenerated
cellulose and any other suitable synthetic fibers known to those
skilled in the art. Synthetic fibers may also include kosmotropes
for product degradation.
Many polyolefins are available for fiber production, for example
polyethylenes such as Dow Chemical's ASPUN.RTM. 6811A linear low
density polyethylene, 2553 LLDPE and 25355 and 12350 high density
polyethylene are such suitable polymers. The polyethylenes have
melt flow rates, respectively, of about 26, 40, 25 and 12. Fiber
forming polypropylenes include Exxon Chemical Company's
Escorene.RTM. PD 3445 polypropylene and Montell Chemical Co.'s
PF-304. Many other polyolefins are commercially available.
Natural fibers include wool, cotton, flax, hemp and wood pulp.
Pulps include standard soft-wood fluffing grade such as CR-1654
from Coosa Mills of Coosa, Ala., high bulk additive formaldehyde
free pulp (HBAFF) available from the Weyerhaeuser Corporation of
Tacoma, Wash., and is a which is a crosslinked southern softwood
pulp fiber with enhanced wet modulus, and a chemically cross-linked
pulp fiber such as Weyerhaeuser NHB-416. HBAFF has a chemical
treatment that sets in a curl and twist, in addition to imparting
added dry and wet stiffness and resilience to the fiber. Another
suitable pulp is Buckeye HP2 pulp and still another is IP Supersoft
from International Paper Corporation. Suitable rayon fibers are 1.5
denier Merge 18453 fibers from Courtaulds Fibers Incorporated of
Axis, Ala.
Various superabsorbents in a number of forms are available.
Commercially available examples include FAVOR.RTM. 870
superabsorbent spheres from the Stockhausen Company of Greensboro,
N.C. 27406 which is a highly crosslinked surface superabsorbent, XL
AFA 94-21-5 and XL AFA-126-15, which are 850 to 1400 micron
suspensions of polymerized polyacrylate particles from The Dow
Chemical Company of Midland, Mich., and SANWET.RTM. IM 1500
superabsorbent granules supplied by KoSA Inc. (formerly Trevira
Inc. and formerly Hoechst-Celanese), PO Box 4, Salisbury, N.C.
28145-0004.
Binders may also be included in the spunbond or airlaid layers in
order to provide mechanical integrity to the web. Binders include
fiber, liquid or other binder means which may be thermally
activated. Preferred fibers for inclusion are those having a
relatively low melting point such as polyolefin fibers. Lower
melting polymers provide the ability to bond the fabric together at
fiber cross over points upon the application of heat. In addition,
fibers having as at least one component a lower melting polymer,
like conjugate and biconstituent fibers, are suitable for the
practice of this invention. Fibers having a lower melting polymer
are generally referred to as "fusible fibers." By "lower melting
polymers" what is meant are those having a glass transition
temperature less than about 175.degree. C. Exemplary binder fibers
include conjugate fibers of polyolefins and/or polyamides, and
liquid adhesives. Two such suitable binders are sheath core
conjugate fibers available from KoSA Inc. under the designation
T-255 and T-256, though many suitable binder fibers are known to
those skilled in the art, and are made by many manufacturers such
as Chisso and Fibervisions LLC of Wilmington, Del. A suitable
liquid binder is Kymene.RTM. 557LX binder available from
Fibervisions LLC.
Once produced, the web must be adequately stabilized and
consolidated in order to retain its shape. The inclusion of a
sufficient amount of fusible fibers and subsequent thermal bonding
is the preferred method for obtaining adequate stabilization. It's
believed that this method allows adequate bonding in the center of
a thick material as well as on the surface.
One example of a product form for a feminine hygiene product for
overnight use, as depicted in FIG. 10; it has an absorbent system
composed of a creped spunbond fabric cover 10, a co-apertured
airlaid intake/distribution layer 11 and a spunbond fabric transfer
delay layer 12, a fluff retention layer 13, and a shaped fluff
perimeter layer 14.
A specific example would be a 13.6 gsm (0.4 osy) spunbond cover,
creped 30 percent to a basis weight of 20.3 gsm (0.6 osy) and
treated with 0.3 weight percent AHCOVEL.RTM. Base N-62 surfactant
and a capillarity fabric made of a co-apertured 175 gsm, 90 weight
percent Weyerhaeuser NF405 and 10 weight percent KoSa T-255 fiber
airlaid fabric at 0.12 g/cc and a 27 gsm (0.8 osy) spunbond
transfer delay layer made of polypropylene. A retention layer made
of 500 gsm fluff, 0.06-0.09 g/cc, of Weyerhaeuser NF-405 is
included. A second retention layer made of 600 gsm fluff, 0.06-0.09
g/cc, of Weyerhaeuser NF-405 is also included.
Under continuous flow conditions, fluid is rapidly absorbed into
the airlaid intake/distribution layer through the wettable and
highly permeable creped spunbond cover. The spunbond fabric
transfer delay layer, which is co-apertured to the airlaid
intake/distribution layer, prevents premature fluid transfer to the
underlying retention layer and forces fluid to distribute
lengthwise in the product.
Its believed by the inventors that Initial insults are absorbed by
and remain in the airlaid intake/distribution layer until 30-40%
saturation levels are achieved (approximately 3-4 grams of fluid).
At this point of saturation in the airlaid intake/distribution
layer, fluid begins to transfer from the intake/distribution layer,
through the transfer delay layer to the underlying fluff retention
layer. The fluff retention layer, centered below the transfer delay
layer, absorbs fluid that passes through the transfer delay layer
as the product is insulted. The transfer delay layer controls the
amount of fluid that is passed to the absorbent below and
facilitates intake/distribution. As the amount of fluid in the
airlaid intake/distribution layer increases, the amount of fluid
transferred through the transfer delay layer to the underlying
fluff increases. By transferring fluid based on the fluid
saturation level, the transfer delay prevents high fluid saturation
levels (>80%) from occurring in the airlaid intake/distribution
layer. This function allows the airlaid intake/distribution layer
to maintain void volume for additional insults. The airlaid
intake/distribution layer returns toward an equilibrium level of
30-40% fluid saturation during use between insults.
While the shape of the various layers is not considered critical to
the success of the invention, it should be noted that the airlaid
intake/distribution and fluff retention layers may also incorporate
a reduced dimension rectangular strip geometry which prevents fluid
from wicking to the pad edges. The combination of
intake/distribution and transfer delay technology, aided to some
degree by the specific material geometry, forces the fluid to
remain in the center of the product in the x, y, and z directions.
The asymmetrical (e.g. hourglass shaped) perimeter layer is also
available to hold fluid under medium to high product fluid loads
(greater than 5 g), but primarily serves as a product shaping
component. It should be noted that the retention layer shape may be
the same as or different from that of the perimeter layer and that
either may have a rectangular, hourglass, racetrack or other shape.
In addition, embossing may be added to the retention and/or
perimeter layer to enhance the integrity of the layer.
The theoretical fluid loading profile for this feminine hygiene
product is illustrated in FIG. 11. FIG. 11 is a graph of the
component liquid content (or loading) in grams on the Y-axis and
total product loading in grams on the X-axis. The airlaid
intake/distribution is depicted by diamonds on the graph, the
retention layer by squares, and the perimeter layer as triangles.
At low loadings (0-3 ml), the fluid is mainly absorbed into the
airlaid intake/distribution layer. As fluid loading increases (3-5
ml), the fluid begins to transfer through the transfer delay layer
into the retention layer and slightly into the perimeter layer. At
this time, very little fluid from additional insults is held in the
airlaid intake/distribution layer. The airlaid intake/distribution
layer continually regenerates its void volume by transferring fluid
to the retention layer so subsequent insults can be accommodated.
At higher loadings (>5 ml), the retention layer holds the
majority of the fluid due to its high void volume. The perimeter
layer has the capacity to retain any residual fluid which is passed
through the retention layer because of localized saturation. The
perimeter layer also provides further coverage for insults outside
of the target area.
Under gush situations (>1 ml/sec and 1-5 ml/insult), the
feminine hygiene product performs similarly to the theoretical
filling profile described above but also demonstrates several
additional functional characteristics. When a gush occurs, it is
absorbed into the void volume of the highly permeable creped cover
and into the airlaid intake/distribution layer. Under gush
situations, the apertures in the airlaid intake/distribution layer
provide internal void volume and increased permeability which
assist intake and storage of fluid. The apertures assist in storage
of fluid by providing an immediate internal reservoir for fluid
until it is absorbed into the surrounding airlaid structure. This
functionality is critical since a gush insult happens so fast that
momentary localized saturation occurs in the un-apertured portions
of the airlaid fabric. During gush insults, the apertures also
provide a direct pathway to the underlying fluff retention layer so
that fluid can be immediately transferred to the fluff layer and
void volume can be quickly regenerated in the airlaid layer. By
regenerating void volume, the airlaid layer is available for future
insults.
Immediately after the gush is absorbed, the intake/distribution and
transfer characteristics of the co-apertured
intake/distribution/transfer delay system take over. The fluid
distributes in the airlaid intake/distribution layer and transfers
through the transfer delay layer until the equilibrium level of
30-40% fluid saturation is achieved in the airlaid
intake/distribution layer. This equilibration process again helps
in regenerating the void volume in the intake/distribution layer so
that it is available to take additional insults. A suitable
intake/distribution layer horizontally wicks menses a distance of
from about 1.2 cm to about 15.25 cm.
Cover Material Properties
It is important that the cover rapidly draw insults into the
product. A number of materials provide such intake properties.
These include pin apertured films, vacuum apertured films,
apertured nonwovens and co-apertured film/nonwoven laminates,
conjugate fiber spunbond fabrics, creped spunbond fabrics, airlaid
fabrics, bonded carded webs, spunlace fabrics, etc. A number of
fabric types which may be unsuitable initially may be made
acceptable through the use of topical chemical treatments and
mechanical processing. Any material which, when combined with an
absorbent core, permits rapid intake, low staining, low rewet and
low fluid retention under all flow conditions would be
suitable.
Creped spunbond nonwoven fabric is preferred as the feminine care
product cover material since it creates benefits that can be
leveraged in the design of a gush management absorbent core. These
benefits are a result of the fundamental property changes that
occur during the creping process. In order to characterize the
structural differences that exist between standard spunbond fabric
and creped spunbond fabric and identify the impact of creping the
spunbond fabric on gush management, two samples are compared. One
sample was a 3.5 dpf, 20.3 gsm (0.6 osy) polypropylene spunbond and
the other was a 3.5 dpf, 13.6 gsm (0.4 osy) polypropylene spunbond
creped 30% to an effective 20.3 gsm basis weight. Both materials
were treated with 0.30 weight percent AHCOVEL surfactant.
Structural differences can be best characterized by comparing the
pore size distributions of the base material to the creped
material. FIG. 8 is a graph of the pore size distribution for these
two samples. In FIG. 8, the Y-axis is the pore volume in cc/g and
the X-axis is pore radius in microns. The creped spunbond fabric is
denoted by the line which peaks first on the left.
The peak pore size for the standard spunbond fabric is 80 microns
while the creped spunbond fabric peak pore size is 170 microns. The
peak pore size increases with creping because, its believed,
primary bonds are deformed and z-directional pores are formed,
thereby creating a three dimensional pore structure. The overall
increase in caliper results in an increase in total pore volume and
a corresponding shift to a larger pore size. For comparison, the
pore structure of standard spunbond fabric is two dimensional due
to its relatively flat surface structure. The increased
permeability and larger pore size of the creped spunbond fabric
allows fluid to enter the product more easily. In addition, the
large pores are better suited for handling the variety of menstrual
fluid types that are associated with heavy and/or gush flow.
The breadth of the pore size distribution also increases with
creping. The area under each of the curves in FIG. 8 represents a
measure of the pore volume for the material. As illustrated by the
curves, the pore volume is much higher for the creped spunbond
fabric compared to the standard spunbond fabric. The increase in
total pore volume facilitates fluid intake and allows the product
to accommodate a variety of flow types without failure. FIG. 9
shows the three dimensional structure of the creped spunbond fabric
cover in an SEM image at a magnification of one inch equals 2
mm.
Additional structural differences between standard and creped
spunbond fabrics are outlined in Table 1. As can be seen from Table
1, the thickness of the creped spunbond fabric is about 2.5 times
that of the uncreped spunbond fabric. The thickness creates a
barrier between the product and the woman's body and promotes skin
dryness by reducing wetness typically caused by rewet. Second, the
permeability of the creped spunbond fabric is significantly higher
than that of the standard spunbond fabric. This increase in
permeability is believed to be due to two factors: the decrease in
spunbond fabric density produced by creping and the partial
orientation of fibers out of the plane of the fabric. Both of these
factors decrease the amount of fiber surface that is in contact
with the testing media and thus provide lower resistance to flow,
again facilitating fast intake.
TABLE 1 Comparison of Structural Properties for Spunbond fabric and
Creped Spunbond fabric Spunbond Creped Spunbond (20.3 gsm, 3.5 dpf)
(20.3 gsm, 3.5 dpf) Thickness 0.254 0.66 (mm) Permeability 511 3953
(Darcies)
The differences in structural properties of the fabrics have a
profound effect on the functional properties that these fabric
exhibit, as described above. Table 2 displays how several
functional properties improve dramatically for the creped spunbond
cover fabric compared to standard uncreped spunbond fabric. Results
are indicative of the contributions of the creped cover alone when
tested over a standard airlaid absorbent core.
TABLE 2 Comparison of Functional Properties for Spunbond and Creped
Spunbond fabric Average Average Average Average Fluid Intake Time
Rewet Stain Size Retention (seconds) (grams) (mm.sup.2) (grams)
Spunbond 32 0.45 751 0.043 (20.3 gsm, 3.5 dpf Creped Spunbond 17
0.07 619 0.015 (20.3 gsm, 3.5 dpf)
The intake time is cut in half due to the increase in permeability
and void volume that is introduced by creping. The creped spunbond
fabric cover results in rewet that is 16% of the rewet that occurs
with the standard spunbond fabric cover. This reduction occurs due
to the increase in permeability, pore size, and thickness of the
creped spunbond fabric cover. The increase in permeability promotes
fluid transport to the absorbent core and the large average pore
size ensures that fluid is not held tightly within the inter-fiber
spacing of the cover, thus being easily desorbed by the absorbent
core. This reduces fluid retention in the cover which reduces rewet
and staining by reducing the amount of fluid that is in contact
with or in close proximity to the top surface of the cover. The
increased loft of the structure provides separation from the
absorbent core and thus provides a barrier to fluid flowback. Some
reduction in stain intensity also occurs due to masking which
occurs as a result of the material thickness.
The functional improvements of faster intake and reduced rewet,
retention, and stain size make the creped spunbond cover an ideal
candidate for incorporation into a gush management absorbent
system. The creped spunbond cover should be light weight,
preferably between about 10 and 30 gsm, more particularly between
about 15 and 25 gsm, with between about 20 and 50 percent creping,
more particularly between about 25 and 40 percent.
Co-apertured Intake/Distribution Layer/Transfer Delay
The intake/distribution layer and the transfer delay layer are
co-apertured using mechanical pin aperturing, though holes may also
be provided by die cutting or forming the materials in such a way
that they are produced with holes in place. The objective is the
production of a material which has regions of high and low
capillarity so as to produce a "capillarity fabric" which
preferentially allows the movement of fluid in some areas but
restricts of prohibits it in others. The fluid transfer delay layer
for personal care absorbent products in accordance with this
invention is designed to enhance distribution in the x-y plane by
delaying the transfer of fluid from the intake/distribution layer
to the retention layer. The preferred form of capillarity fabric is
produced by the co-aperturing of an airlaid fabric and spunbond
fabric, though an apertured nonwoven fabric or an embossed nonwoven
fabric may also function well. The co-aperturing of the
intake/distribution and transfer delay layers provides unique
characteristics for the management of gush insults. A unique
material is created with a tri-modal pore structure consisting of
1) pores in the bulk of the airlaid which are characteristic of the
original structure in the case of airlaid materials, 2) large void
spaces defined by the pins of the aperturing process, and 3) small
interfacial pores surrounding the perimeter of the apertures. The
apertures are typically characterized by an open structure which
tapers into a rounded cone-like structure as observed from the
airlaid side of the composite. The interfacial pores are smaller
than the surrounding pores due to densification and fiber
relocation which results from the aperturing process.
The transfer delay layer provides a permeability and wettability
gradient between the intake/distribution layer and the underlying
retention layer by preventing intimate contact between the two
layers. The transfer delay layer should have relatively low
permeability and wettability so it will promote lateral fluid
distribution in the intake/distribution layer under continuous flow
conditions and so control fluid movement in the Z-direction. The
wettability of the transfer delay layer may be modified by topical
chemical treatments known to those skilled in the art to affect the
hydrophobicity of a material. Some suitable chemicals for
modification of wettability are marketed under the tradenames
AHCOVEL.RTM., Glucopon.RTM., Pluronics.RTM., Triton.RTM., and Masil
SF-19.RTM.. The transfer delay promotes lateral (X-Y) distribution
in the intake/distribution layer resulting in fluid accumulation in
the intake/distribution layer, and then allows fluid transfer to
the retention layer when high pressures or high saturation levels
occur. It is believed by the inventors that fluid does not
preferentially move into the apertures under continuous flow
conditions. This controlled transfer mechanism results in an
elongated stain pattern in the retention layer and prevents
over-saturation in the insult area and provides a visual signal for
the wearer indicating product life remaining.
Under gush flow conditions, the apertures in the transfer delay
layer allow fluid to immediately pass through to the underlying
retention layer.
FIG. 2 illustrates the tri-modal pore structure of the co-apertured
material. In FIG. 2, three classes of pores are illustrated. Large
pores 1 are located at the point where the fabric was apertured.
Smaller pores 2 exist in the original airlaid fabric 4. Yet another
class of pores 3 may be found in the area surrounding the point
where the fabric was apertured due to densification of the fabric
and fiber relocation during the aperturing process.
FIGS. 3, 4, and 5 display SEM images of the apertures. FIG. 3
displays an aperture on the airlaid side of the composite at a
magnification of one inch (2.54 cm) equals 1 mm. FIG. 4 displays a
close-up of an aperture on the airlaid side of the composite at a
magnification of one inch equals 200 microns and FIG. 5 displays an
aperture from the spunbond side of the composite at a magnification
of one inch equals 2 mm.
FIG. 6 compares the pore size distribution of an apertured airlaid
material to a un-apertured airlaid material. In FIG. 6 the
un-apertured airlaid material is signified by the large dark
squares and the apertured (at a pin density of about 2.5
pins/cm.sup.2) airlaid material by the lighter colored diamonds.
The pore volume (cc/g) is on the Y-axis and the pore radius
(microns) on the X-axis. This graph indicates that there is a
slight shift toward smaller pores with the apertured material. This
is due to a slight densification of the material around the
apertures. The large pores which are created by the apertures are
not represented in the graph due to their large size. They do,
however, provide additional void volume for the material.
FIG. 7 illustrates the detail of a single aperture in relation to
the functionality of the absorbent composite. In FIG. 7 an insult
(noted by arrows) is delivered to a cover 1. The insult flows
through the cover 1 to the co-apertured laminate of the invention
where it passes though the intake/distribution layer 2 either at
the aperture 3 or through the layer 2 itself. The insult may also
be distributed laterally along its length to other areas 5 within
the intake/distribution layer 2. Much of the insult eventually
passes through the intake/distribution layer 2 and transfer delay
layer 6 to the absorbent retention core 4.
The functionality of the co-apertured system can be broken down
into five areas: cover desorption, increased surface area, aperture
void volume, access to fluff, and wicking capability. Each of these
functionality benefits is discussed individually below.
1. Cover Desorption
The un-apertured areas of the intake/distribution layer material
maintain a high degree of capillarity after insult and are well
suited for desorbing the liner. The small pores of the preferred
airlaid material provide the capillarity necessary to desorb the
large pores of the cover, thereby removing a majority of fluid from
the surface of the product. Improved cover desorption results in
low smearing and cover staining levels.
2. Increased Surface Area
The apertured areas of the intake/distribution layer material
provide increased surface area for the absorption of fluid. During
gush insults, fluid that contacts an aperture can be absorbed in
the x, y, and z directions through the wall of the aperture, rather
than strictly in the z-direction through the top surface.
Therefore, the increased surface area provided by the walls of the
apertures enhances the intake characteristics of the airlaid
absorbent layer. Additionally, the apertures increase the overall
permeability of the intake/distribution layer.
3. Aperture Void Volume
The open areas and void volume created by the apertures allow fluid
to be accumulated internally in the product before absorption into
the intake/distribution layer material itself. This prevents
pooling on the pad surface and facilitates intake when localized
saturation of the intake/distribution layer prohibits immediate
fluid intake.
4. Access to retention layer
The apertures in the intake/distribution layer material provide a
direct fluid pathway to the fluff in the apertured areas. Under
gush flow conditions, fluid passes directly through the aperture
and into the retention layer. By providing immediate access to
retention capacity under these conditions, the void volume of the
intake/distribution layer is maintained and intake times for
multiple insults are reduced.
5. Wicking Capability
When the intake/distribution layer material is the preferred
airlaid fabric, its stability and high degree of wet integrity do
not allow the pores to collapse to an appreciable degree when the
product is insulted. The stable pore structure allows capillary
wicking to laterally transport the fluid out of the insult area and
into other regions of the product. The un-apertured areas of the
airlaid material maintain this functionality and capillary wicking
prevents high saturation from occurring in the insult area.
Capillary wicking in combination with the stability of the material
allows void volume to be regenerated after an insult so that
additional insults can be accepted.
Experiments were undertaken to examine preferred forms of the
invention. Three different basis weights of airlaid fabrics were
evaluated: 100, 175, and 250 gsm. Comparisons were made between the
three apertured airlaid fabric samples and an un-apertured control
sample. The aperturing pattern in FIG. 12 was used initially and
had 48 pins/inch.sup.2 (7.4 pins/cm.sup.2) using 0.081" (2.06 mm)
diameter pins.
These materials were tested over a fluff absorbent core using the
flat system fluid distribution test. Key measurements included
stain size, whether the saturation profile was even or skewed, and
the amount of fluid retention and transfer in the airlaid layer.
These results are summarized in Table 3.
TABLE 3 Flat System Fluid distribution test - Co-apertured Material
Matrix Apertured* Apertured* Apertured* Control 100 gsm, 175 gsm,
250 gsm, 250 gsm, 0.06 g/cc, 0.08 g/cc, 0.14 g/cc, 0.14 g/cc, 80/20
88/12 90/10 90/10 Stain Size 12.7 cm 10.2 cm 10.2 cm 15.2 cm
Saturation Even Profile Even Profile Even Profile Even Profile
Retention 3.5 g 3.8 g 3.0 g 4.5 g Transfer 2.5 g 2.3 g 3.0 g 1.5 g
*The densities reflected above are pre-apertured densities, the
densities of the apertured materials are higher.
This testing showed a decrease in stain length as well as fluid
retention in the apertured samples, compared to the control,
indicating that aperturing the airlaid fabric increases the density
of the airlaid fabric dramatically because the pin density of the
initial aperturing pattern (FIG. 12) was so high. This is most
noticeable on high basis weight, high original density samples. As
the density increases, the pore size and void volume of the fibrous
regions of the airlaid materials decrease.
As a result of this sample testing, it was determined that
aperturing had the potential to impact product performance. Further
testing was performed at a pin density of 16 pins/inch.sup.2 (2.5
pins/cm.sup.2) (shown in FIG. 13) to minimize increases in
post-aperturing material density. The pin diameter remained at
0.081". The range of fabric density studied was narrowed to 175 to
200 gsm and the airlaid fabric was co-apertured to a spunbond
fabric transfer delay layer to maintain the intake/distribution
functionality.
Tables 4 and 5 display the additional material matrices that were
evaluated. The transfer delay layers were spunbond polypropylene
fabrics except where film is indicated. The spunbond transfer delay
layers had a density and basis weight as indicated. The spunbond
fabrics were not treated with surfactants so remained naturally
non-wettable. The film was a 1 mil thick polyethylene film.
TABLE 4 Co-apertured Airlaid Material/Transfer Delay Layer Basis
Weight Density Transfer Delay Layer 175 gsm 0.08 g/cc 27 gsm 175
gsm 0.08 g/cc 33.9 gsm 175 gsm 0.10 g/cc 27 gsm 175 gsm 0.10 g/cc
33.9 gsm
TABLE 5 Co-apertured Airlaid Material/Transfer Delay Layer Basis
Weight Density Transfer Delay Layer 175 gsm 0.12 g/cc 27 gsm 175
gsm 0.14 g/cc 33.9 gsm 200 gsm 0.12 g/cc 27 gsm 200 gsm 0.12 g/cc
33.9 gsm 200 gsm 0.12 g/cc Film 200 gsm 0.14 g/cc 27 gsm 200 gsm
0.14 g/cc 33.9 gsm 200 gsm 1.14 g/cc Film
The materials described in Tables 4 and 5 represent materials which
were believed to have better performance characteristics potential
due to lower aperturing pin density and lower basis weight and/or
starting densities. These materials were tested for capacity,
horizontal wicking capability, saturation capacity, fluid
partitioning characteristics, and triple intake gush capability.
Each of these areas is discussed individually below. As a result of
this testing, its believed that the pin density should be between
about 10 and 40 pins/inch.sup.2 (1.6 and 6.2 pins/cm.sup.2) for
good performance.
Capacity
FIG. 14 shows the measured capacity for airlaid fabrics with and
without apertures. In FIG. 14, the top line represents the 175 and
200 gsm, un-apertured airlaid fabrics, the middle line a 200 gsm
co-apertured airlaid fabric, and the bottom line a 175 gsm
co-apertured fabric. Capacity decreases with increasing density as
expected. Capacity is also slightly reduced for the apertured
samples. This data reveals that an apertured airlaid fabric at 200
gsm and 0.14 g/cc has an equivalent capacity to an un-apertured 175
gsm, 0.14g/cc fabric.
Horizontal Capillary Wicking--Infinite Reservoir
Horizontal capillary wicking testing was completed to assess the
effect of the aperturing process on horizontal wicking distance.
Horizontal wicking distance is important to maintain a visual
signal which alerts the wearer that the product is nearing capacity
and should be replaced. Without appropriate wicking functionality,
the visual signal is not present to the desired degree.
The horizontal capillary wicking results of the 175 gsm low density
airlaid samples of Table 4 indicate that aperturing the airlaid
material reduces capillary wicking distance. Its believed that the
aperturing process creates apertures which disrupt the fluid
pathway for wicking and creates density gradients around each
aperture. The apertured materials wicked between 17 and 30 mm less
than the un-apertured samples, depending on original density. A
larger difference existed for materials which had a higher starting
density. These results are shown in FIG. 15 where wicking distance
in mm is shown on the y-axis and time in minutes on the x-axis. In
FIG. 15, the 33.9 gsm un-apertured fabric is the highest line,
immediately below it is the line for the 27 gsm un-apertured
fabric, followed by the 27 gsm apertured fabric and the 33.9 gsm
apertured fabric.
FIG. 15 also indicates that the wicking path disruption associated
with aperturing has more impact on horizontal wicking performance
than the effect of increased airlaid density. This indicates that
the aperturing effect is not a simple densification effect. The
horizontal wicking results indicate that there is capillary
discontinuity in the apertured samples which results in a
significant wicking path disruption.
In an effort to improve wicking distance, higher density airlaid
fabric samples were apertured and their capillary wicking
performance evaluated. Again the results indicate that the higher
density apertured samples do not wick as far as the un-apertured
control material. This further showed that capillary disruption is
a result of the aperturing process and indicates that capillary
wicking distance cannot be controlled by density in the apertured
materials.
Wicking Saturation Capacity
To assess the saturation level that results after the capillary
wicking process, the saturated materials were sectioned and
weighed. The gram per gram saturation level was then calculated to
determine how the aperturing process affects the overall gram per
gram capacity level of the materials. Note that these saturation
levels are based on capillary wicking and not on a dunk and drip
protocol.
FIG. 16 displays the effect of aperturing on saturation level for
the 175 gsm low density airlaid samples of Table 4. The results
indicate that not only does horizontal wicking distance decrease as
a result of the aperturing process, but wicking saturation capacity
decreases also. The apertured samples are much less saturated than
the un-apertured samples regardless of starting density though no
significant differences were noted between samples that had
different starting densities. The effect of aperturing was appeared
to be more dominant than the effect of starting density. In FIG.
16, the saturation in g/g is indicated on the y-axis and the
wicking distance in inches on the x-axis. The upper most line
represents the un-apertured 0.1 g/cc sample, the line below the
0.08 g/cc un-apertured sample, the next line down represents the
0.08 g/cc co-apertured sample and the lowest line the 0.1 g/cc
co-apertured sample. All samples are 175 gsm.
The effect of aperturing on the capillary wicking saturation of
higher density airlaid materials was also assessed. Again, the
apertured samples had lower gram per gram saturation levels than
the un-apertured control. It thus appears that basis weight had a
minimal effect on horizontal wicking distance or saturation level
of the co-apertured samples. The 175 and 200 gsm samples perform
similarly and only slight differences were noticed between
densities. Overall wicking distance was the same for 0.12 and 0.14
g/cc samples, but the saturation level of the 0.12 g/cc samples was
higher, believed to be attributable to the higher void volume of
the 0.12 g/cc samples.
Horizontal Capillary Wicking--Demand Absorbency
The objective of aperturing and/or co-aperturing is to increase
fluid handling of gush flow while maintaining appropriate fluid
intake/distribution and wicking characteristics. Infinite reservoir
horizontal wicking tests discussed above have shown that capillary
wicking capability and saturation capacity are affected by the
aperturing process. Since products experience a variety of
pressures and flow conditions in use, wicking potential under
demand absorbency was also studied. In the demand absorbency
horizontal wicking test, the flat system fluid distribution test
method is used and fluid is introduced into the product at a rate
of 10 ml/hr.
The results showed that the materials are evenly saturated
throughout their length, indicating that wicking is not decreased
by aperturing in a demand absorbency wicking setting. Its believed
that the stable structure of the airlaid fabric allows the
apertured airlaid fabric to be fully utilized even though it does
not have the continuous capillary fluid paths that are found in an
un-apertured airlaid fabric.
Fluid Partitioning Characteristics Under Demand Absorbency
Conditions
FIGS. 17 and 18 show the results of a test of the fluid
partitioning characteristics of the material. In FIGS. 17 and 18,
the cover layer is indicated by a light colored vertical bar, the
intake/distribution layer by a dark bar and the fluff perimeter
layer by a white bar. In these Figures, the y-axis is the
saturation in g/g and the x-axis is the pad section distance from
the front edge. The test was carried out at by delivering 5 ml at a
rate of 10 mls/hr and under a pressure of 0.25 psi. Fluid
partitioning is important in assessing how co-aperturing the
airlaid and transfer delay layers changes the fluid transfer
characteristics of the product. Ideally, fluid should distribute
throughout the entire length of the airlaid layer and transfer
though the transfer delay layer simultaneously.
FIG. 17 shows that the control system (un-apertured 175 gsm, 0.14
g/cc airlaid layer using 27 gsm spunbond transfer delay layer) does
not allow any fluid transfer to the fluff perimeter layer of the
product. FIG. 18 shows that the co-apertured sample (co-apertured
175 gsm, 0.14 g/cc airlaid layer using 0.8 osy spunbond transfer
delay layer) does allow transfer to the perimeter fluff layer.
Triple Intake Times
Triple intake testing was completed on a number of airlaid
materials to assess the effects of co-aperturing on the intake
rates of materials with different starting densities and different
transfer delay layers. Testing was done using 3, 2 ml insults, 9
minutes apart. In all of the bar graphs of triple intake testing,
the first insult is indicated by a light colored bar, the second in
a dark bar and the third in a white bar. The airlaid fabric used in
the samples for FIGS. 19 and 20 were made from 90 weight percent
NB416 pulp and 10 weight percent Hoescht-Celanese T-255 binder
fiber. In FIGS. 19, 20 and 21, the y-axis is the intake time in
seconds.
In FIG. 19, the samples, moving from left to right are 175 gsm,
0.10 g/cc apertured airlaid fabric over fluff, 175 gsm, 0.10 g/cc
un-apertured airlaid fabric with a 27 gsm spunbond transfer delay
layer over fluff, 175 gsm 0.08 g/cc co-apertured airlaid fabric
with a 27 gsm spunbond transfer delay layer over fluff, 175 gsm
0.08 g/cc co-apertured airlaid fabric with a 33.9 gsm spunbond
transfer delay layer over fluff, 175 gsm 0.10 g/cc co-apertured
airlaid fabric with a 27 gsm spunbond transfer delay layer over
fluff, 175 gsm 0.10 g/cc co-apertured airlaid fabric with a 33.9
gsm spunbond transfer delay layer over fluff. In FIG. 20, the
samples, moving from left to right are 200 gsm, 0.14 g/cc apertured
airlaid fabric over fluff, 200 gsm, 0.14 g/cc un-apertured airlaid
fabric with a 27 gsm spunbond transfer delay layer over fluff, 200
gsm 0.14 g/cc co-apertured airlaid fabric with a 33.9 gsm spunbond
transfer delay layer over fluff, 200 gsm 0.14 g/cc co-apertured
airlaid fabric with a 27 gsm spunbond transfer delay layer over
fluff, 200 gsm 0.14 g/cc co-apertured airlaid fabric with a 1 mil
film delay layer over fluff, 200 gsm 0.12 g/cc co-apertured airlaid
fabric with a 1 mil film transfer delay layer over fluff, 200 gsm
0.12 g/cc co-apertured airlaid fabric with a 27 gsm spunbond
transfer delay layer over fluff and 200 gsm 0.12 g/cc co-apertured
airlaid fabric with a 33.9 gsm spunbond transfer delay layer over
fluff.
FIGS. 19 and 20 below show that triple intake times are similar for
all of the co-apertured materials tested regardless of which
transfer delay layer was used and what density the airlaid fabric
was. Triple intake times are higher than a standard airlaid/fluff
system and are lower than the same system with a transfer delay but
without aperturing. These results indicate that the immediate
access to the underlying fluff layer has been greatly improved by
co-aperturing.
Triple Intake Testing on a complete gush management absorbent
system with a creped cover and co-apertured absorbent system
indicate the individual effects of each component.
FIG. 21 displays the triple gush intake results. In FIG. 21, the
samples, moving from left to right are creped spunbond fabric cover
with 175 gsm 0.12 g/cc co-apertured airlaid fabric with a 27 gsm
spunbond transfer delay layer over fluff, un-creped spunbond fabric
cover with 175 gsm 0.12 g/cc co-apertured airlaid fabric with a 27
gsm spunbond transfer delay layer over fluff, creped spunbond
fabric cover with 175 gsm 0.12 g/cc un-apertured airlaid fabric
with a 27 gsm spunbond transfer delay layer over fluff, and
uncreped spunbond fabric cover with 175 gsm 0.12 g/cc un-apertured
airlaid fabric with a 27 gsm spunbond transfer delay layer over
fluff.
The results indicate that combining the creped spunbond cover with
a co-apertured intake/distribution/transfer delay layer decreases
the intake times and facilitates quicker intake than all of the
other samples. It can also be seen from this data that the samples
with the creped spunbond cover performed better than the samples
with the regular spunbond cover. Co-aperturing made a smaller
contribution than did the choice of cover but additional
improvements were seen when the creped cover and the co-apertured
system were combined. The faster intake times are believed to be a
result of the increased fluid transfer to the fluff layer and the
void volume that is generated in the intake/distribution layer as a
result of this.
The results reveal that the intake/distribution layer should be an
airlaid fabric between about 150 and 300 gsm, more particularly
between about 175 and 225 gsm, with a density between about 0.05
and 0.18 g/cc, more particularly between about 0.08 and 0.14 g/cc.
The transfer delay should be a film, meltblown fabric or spunbond
fabric, more particularly a spunbond fabric with a basis weight
between about 15 and 50 gsm, still more particularly between about
25 and 35 gsm.
Although only a few exemplary embodiments of this invention have
been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims. In the claims, means
plus function claims are intended to cover the structures described
herein as performing the recited function and not only structural
equivalents but also equivalent structures. Thus although a nail
and a screw may not be structural equivalents in that a nail
employs a cylindrical surface to secure wooden parts together,
whereas a screw employs a helical surface, in the environment of
fastening wooden parts, a nail and a screw may be equivalent
structures.
It should further be noted that any patents, applications or
publications referred to herein are incorporated by reference in
their entirety.
* * * * *